What are all those choppers doing in my back yard?

[Aspidistra]

Seriously, about 30 big black helicopters have flown over my house in the last half hour. And they're still coming (sporadically)

I search in the news, and Google, but I'm not seein nuthin.

The Internets have failed me! I turn to dopers. What on earth could be going on?

[Cunctator]

From The Age (13 March): link

It looks like it's been happening around Melbourne for the past few days, and continues until tomorrow.

[Aspidistra]

yep, that would be it!

It's taken them a while to get round to the inner city then. Maybe it's too easy to need practising...